This invention relates to a printing apparatus and a printhead characteristic data selection method and, more particularly, to a printing apparatus having, e.g., an inkjet printhead, and a printhead characteristic data selection method.
As is already well known, an inkjet printhead (hereinafter referred to as a printhead) has a construction such that a plurality of ink discharge nozzles (hereinafter referred to as nozzles) are arranged at a constant density.
When printing, particularly halftone image printing, is performed with a printhead of this type, density unevenness might occur in a printed image due to an uneven amount of ink discharged from each of the nozzles, or uneven adhered positions of ink droplets discharged on a print medium.
Such density unevenness results from different printing characteristics of each printhead. In order to improve printing quality, it is necessary to reflect printing characteristic data, corresponding to each printhead, to printing operation. In view of this, a conventional printhead includes a non-volatile memory (e.g., EEPROM or the like) for storing characteristic data unique to each printhead, so that when the printhead is mounted on a printing apparatus, the characteristic data is read out of the memory by the printing apparatus.
However, a printhead having a non-volatile memory raises a problem of a high cost compared to a printhead not having a non-volatile memory.
To cope with this problem, conventionally, in a printing apparatus which no longer requires exchange of a deteriorated printhead by virtue of improved performance of a printhead, the characteristic data is stored not in a printhead, but in a non-volatile memory (EEPROM or the like) of the printing apparatus main unit so as to eliminate a storage medium from the printhead, thereby preventing an increased cost of the printhead.
However, in this case, unlike the structure in which the characteristic data is stored only in a printhead, there are various places or combinations of places to store the characteristic data, e.g., in a printing apparatus main unit, host computer, printing apparatus main unit and host computer, printhead and printing apparatus main unit, or the like. The most appropriate way of handling the printhead characteristic data still leaves a room for further improvement.
Accordingly, it is an object of the present invention to provide a printing apparatus and printhead characteristic data selection method, which can appropriately handle printhead characteristic data under various environments.
According to one aspect of the present invention, the foregoing object is attained by providing a printing apparatus comprising: judgment means for judging whether or not there is at least one medium or external device which stores characteristic data of a printhead; input means for inputting the characteristic data of the printhead from the at least one medium or external device in accordance with a predetermined priority order, based on a judgment result of the judgment means; storage means for storing the characteristic data; and printing means for performing printing by driving the mounted printhead with use of the characteristic data inputted by the input means or stored in the storage means.
The above-described apparatus may further comprise determination means for determining validity of the characteristic data each time the characteristic data of the printhead is inputted by the input means in accordance with the predetermined priority order.
The above-described apparatus may further comprise selection means for selecting one of the characteristic data of the mounted printhead or average printhead characteristic data stored in the storage means, based on the judgment result of the judgment means or determination result of the determination means.
Herein, the at least one medium or external device is a non-volatile memory of the printhead, host computer, or non-volatile memory of the printing apparatus.
Further, (1) in a case where the characteristic data of the mounted printhead is stored in all of the non-volatile memory of the printhead, host computer, and non-volatile memory of the printing apparatus, a first rank is assigned to the non-volatile memory of the printhead, a second rank is assigned to the non-volatile memory of the printing apparatus, and a third rank is assigned to the host computer as the predetermined priority order; whereas (2) in a case where the characteristic data of the mounted printhead is stored in the non-volatile memory of the printhead and non-volatile memory of the printing apparatus, a first rank is assigned to the non-volatile memory of the printhead and a second rank is assigned to the non-volatile memory of the printing apparatus as the predetermined priority order.
Furthermore, (1) in a case where the judgment means judges that the characteristic data of the printhead is not stored in any of the printhead, host computer, or non-volatile memory of the printing apparatus, or (2) in a case where the determination means determines that the characteristic data of the printhead is invalid, the selection means selects the average printhead characteristic data stored in the storage means.
The aforementioned printhead is an inkjet printhead, which performs printing by discharging ink, and preferably comprises an electrothermal transducer, which generates heat energy to be applied to ink, for discharging ink by utilizing the heat energy.
Furthermore, the aforementioned non-volatile memory includes EEPROM or the like.
According to another aspect of the present invention, the foregoing object is attained by providing a method of selecting characteristic data of a printhead comprising the steps of: judging whether or not there is at least one medium or external device which stores characteristic data of a printhead mounted to a printing apparatus; and inputting the characteristic data of the printhead from the at least one medium or external device in accordance with a predetermined priority order, based on a judgment result at the judgment step.
The above-described method may further comprise the step of determining validity of the characteristic data each time the characteristic data of the printhead is inputted at the input step in accordance with the predetermined priority order.
The above-described method may further comprise the step of selecting one of the characteristic data of the printhead or average printhead characteristic data stored in a storage medium provided in the printing apparatus, based on the judgment result at the judgment step or determination result at the determination step.
In accordance with the present invention as described above, judgment is made as to whether or not there is at least one medium or external device which stores characteristic data of a printhead mounted to a printing apparatus; the printhead characteristic data is inputted from the at least one medium or external device in accordance with a predetermined priority order based on the judgment result; validity of the characteristic data is determined each time the printhead characteristic data is inputted in accordance with the predetermined priority order; and selection is made from the printhead characteristic data and average printhead characteristic data, stored in a storage medium provided in the printing apparatus, based on the judgment result or determination result.
The invention is particularly advantageous since most appropriate printing operation can be performed by acquiring printhead characteristic data most appropriate for a current condition regardless of where the printhead characteristic data is stored.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.